Positive electrode material and nickel-zinc battery

ABSTRACT

The present invention provides a nickel-zinc battery of an inside-out structure, that is, a battery comprising a positive electrode containing beta-type nickel oxyhydroxide and a negative electrode containing zinc and having a similar structure to an alkali manganese battery, in which the beta-type nickel oxyhydroxide consists of substantially spherical particles, mean particle size of which is within a range from l9 μm to a maximum of 40 μm, the bulk density of which is within a range from 1.6 g/cm 3  to a maximum of 2.2 g/cm 3 , tap density of which is within a range from 2.2 g/cm 3  to a maximum of 2.7 g/cm 3 , specific surface area which based on BET method is within a range from 3 m 2 /g to a maximum of 50 m 2 /g, and the positive electrode of the nickel zinc battery contains graphite powder, where the weight ratio of graphite powder against a total weight of the positive electrode is defined within a range from 4% to a maximum of 8%.

RELATED APPLICATION DATA

[0001] The present application claims priority to Japanese ApplicationNo. P2000-121339 filed Apr. 21, 2000, P2000-145601 filed May 17, 2000and P2001-060394 filed Mar. 5, 2001, which applications are incorporatedherein by reference to the extent permitted by law.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to beta-type nickel oxyhydroxideand a method of producing thereof, and yet, also relates to a positiveelectrode active material composed of beta-type nickel oxyhydroxide.Further, the present invention relates to a nickel-zinc batteryincorporating a positive electrode comprising beta-type nickeloxyhydroxide as a positive electrode active material and a negativeelectrode comprising zinc as a negative electrode active material.

[0003] In recent years, compact-size portable electronic apparatuses,especially portable game players, digital cameras and digitalvideo-camera recorders, or the like, have been propagated verysignificantly. It is expected that these compact-size portableelectronic apparatus will be propagated furthermore from now on, andthus, demand for compact-size battery serving as a power-supply sourcefor these compact-size portable electronic apparatuses will also bepromoted quickly. Generally, any of those compact-size portableelectronic apparatuses utilizes a high operating voltage and requires alarge amount of current, and thus, a usable power source must bedistinguished in discharge characteristic under heavy load.

[0004] Of those batteries satisfying the above requirements, such aalkaline-manganese battery has already been propagated most widely,which comprises manganese dioxide for composing the positive electrodeand zinc for the negative electrode, and yet, it also comprises highlyconcentrated alkaline aqueous solution for composing electrolyticsolution. Inasmuch as manganese dioxide and zinc are respectivelyinexpensive, and yet, because of high energy density per weight, notonly for the power-supply source of compact-size portable electronicapparatuses, but the alkaline-manganese battery is also utilizedextensively.

[0005] Considering further utility for compact-size portable electronicapparatuses and in order to further improve discharge characteristicunder heavy load, a wide variety of improvements have been achieved in arange from battery material to the composition of battery itself.However, in the above alkaline-manganese battery, inasmuch as a positiveelectrode active material comprising manganese dioxide performsdischarge based on homogeneous solid-phase chemical reaction, as aresult of discharge, voltage gradually lowers whereby drawing such adischarge curve of downward-sloping. Because of this, in such acompact-size portable electronic apparatus requiring a high voltage anda large amount of current, basically, discharge performance of thealkaline-manganese battery can hardly suffice practical need, and yet,despite of a variety of improvements thus far effected, duration ofactually operable capacity of such a compact-size portable electronicapparatus has thus been extended by a negligible extent. Further, any ofthe modern compact-size portable electronic apparatuses is apt toperform own operation with a relatively higher voltage and a greateramount of current in the initial stage of distribution in the market. Todeal with this tendency, it is imperative that such a battery compatiblewith a newer model of any of compact-size portable electronicapparatuses and capable of preserving distinguished durability to heavyload be provided as essential requirements.

[0006] To suffice the above requirements, a nickel-zinc battery has thusbeen proposed. The nickel-zinc battery comprises its positive electrodecomprising nickel oxyhydroxide and its negative electrode comprisingzinc, which contains such an operating voltage and durability to heavyload respectively being higher than those of the abovealkaline-manganese battery. On the other hand, nickel oxyhydroxide as apositive electrode active material easily generates oxygen and a largeamount of self-discharge as problems to solve. As a method for solvingthese problems, for example, the Japanese Laid-Open Patent PublicationNo. HEISEI-10-214621 (1998) proposes such a nickel-zinc battery havingan “inside-out” type structure with a less amount of self-discharge byutilizing gamma-type nickel oxyhydroxide (γ-NiOOH) for composing apositive electrode active material.

[0007] Such a battery utilizing the above-cited gamma-type nickeloxyhydroxide has a small amount of self-discharge, and has higheroperating potential than that of an alkaline manganese battery. However,it is a problem that such a battery cannot have large discharge capacitybecause the above gamma-type nickel oxyhydroxide has relatively lowdensity.

SUMMARY OF THE INVENTION

[0008] The object of the present invention is to provide such anickel-zinc battery having such a discharge voltage higher than that ofan alkaline-manganese battery and distinguished in the large-currentdischarge characteristic.

[0009] The present invention introduces such a positive electrode activematerial comprising beta-type nickel oxyhydroxide consisting ofsubstantially spherical particles. Preferably, mean particle size of thebeta-type nickel oxyhydroxide is within a range from 19 μm to a maximumof 40 μm. Preferably, bulk density of the beta-type nickel oxyhydroxideis within a range from 1.6 g/cm³ to a maximum of 2.2 g/cm³. Preferably,tap density is within a range from 2.2 g/cm³ to a maximum of 2.7 g/cm³.Preferably, specific surface area of beta-type nickel oxyhydroxide basedon BET method is within a range from 3 m²/g to a maximum of 50 m²/g.

[0010] The above-referred beta-type nickel oxyhydroxide for composingthe positive electrode active material used for implementing the presentinvention is previously treated with alkaline aqueous solution andcontains alkaline cation between layers of the beta-type nickeloxyhydroxide.

[0011] Further, the nickel-zinc battery proposed by the presentinvention utilizes the above-referred beta-type nickel oxyhydroxide forcomposing positive electrode active material. The positive electrode atleast contains beta-type nickel oxyhydroxide and graphite powder, wherethe weight ratio of graphite powder against a total weight of thepositive electrode is defined within a range from 4% to a maximum of 8%.

[0012] According to the present invention, it is possible to secure suchnickel oxyhydroxide with least self-discharge, and yet, such anickel-zinc battery using said nickel oxyhydroxide for composingpositive electrode active material as the one embodied by the inventiongenerates such an operating voltage and distinguished durability toheavy load respectively being higher than those of conventionalalkaline-manganese batteries.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a vertical cross-sectional view of a nickel-zinc batteryaccording to a practical form for embodying the present invention;

[0014]FIG. 2 is explanatory of substantially spherical beta-type nickeloxyhydroxide (A) realized by the present invention and conventionalnon-spherical beta-type nickel oxyhydroxide (B);

[0015]FIG. 3 exemplifies grading distribution of the beta-type nickeloxyhydroxide according to a practical form for embodying the presentinvention;

[0016]FIGS. 4A to 4D exemplify the relationship between the compositionof potassium in nickel oxyhydroxide after completing a process fortreating the beta-type nickel oxyhydroxide with aqueous solution ofpotassium hydroxide and the diffraction figure of powder via X-rayanalysis;

[0017]FIG. 5 exemplifies discharge curve when sample batteries 1˜4 eachcontaining 1500 mW of power executed discharge down to 1.0 V;

[0018]FIG. 6 exemplifies results of testing digital cameras loaded withsample batteries 1 to 4;

[0019]FIG. 7 exemplifies the relationship between specific surface areaand discharge capacity of the positive electrode active material shownby sample batteries 5 to 20;

[0020]FIG. 8 exemplifies the relationship between specific surface areaand discharge capacity of the positive electrode active material shownby sample batteries 21 to 24,

[0021]FIG. 9 exemplifies the relationship between specific surface areaand discharge capacity of the positive electrode active material shownby sample batteries 25 to 28;

[0022]FIG. 10 exemplifies the relationship between specific surface areaand discharge capacity of the positive electrode active material shownby sample batteries 29˜39;

[0023]FIG. 11 is a table showing compositions of the sample batteries 1to 4;

[0024]FIG. 12 is a table showing discharge capacities of the samplebatteries 1 to 4;

[0025]FIG. 13 is a table showing the classification and the batteryproperties of the sample batteries 5 to 28;

[0026]FIG. 14 is a table showing processing conditions for the samplebatteries 29 to 39;

[0027]FIG. 15 is a table showing compositions of the sample batteries 29to 39;

[0028]FIG. 16 is a table showing discharge capacities of the samplebatteries 29 to 39 before storage;

[0029]FIG. 17 is a table showing discharge capacities of the samplebatteries 29 to 39 after storage;

[0030]FIG. 18 is a table showing compositions of the sample batteries 40to 48;

[0031]FIG. 19 is a table showing discharge capacities of the samplebatteries 40 to 48; and

[0032]FIG. 20 exemplifies the relationship between graphite contents inthe positive-polar composing material and discharge capacity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Practical forms for implementing the present invention inrelation to beta-type nickel oxyhydroxide and method of producing thenickel oxyhydroxide, a positive electrode active material, and anickel-zinc battery, are described below.

[0034]FIG. 1 is a vertical cross-sectional view of a nickel-zinc battery1 as an example of a battery according to an embodiment of the presentinvention. The nickel-zinc battery 1 comprises the following: a batterycan 2, a positive electrode 3, a separator 4, a negative electrodemixture 5, a sealing member 6, a washer 7, a negative electrode terminalplate 8, and a current collecting pin 9.

[0035] The battery can 2 is made of iron plated with nickel, forexample, which constitutes an external positive electrode terminal ofthe nickel-zinc battery 1.

[0036] The positive electrode 3 is of a hollow cylindrical form.Beta-type nickel oxyhydroxide, graphite powder as electricallyconductive agent, and electrolytic aqueous solution of potassium hydridejointly formulate positive electrode mixture. The positive electrodemixture is molded into a hollow cylindrical form to prepare positiveelectrode pellets 3 a, 3 b, and 3 c, which are serially laminated insideof the battery can 2.

[0037] The separator 4 is of hollow cylindrical form and disposed insideof the positive electrode 3.

[0038] The negative electrode mixture 5 comprises zinc particles forcomposing a negative electrode active material, electrolytic solutionusing aqueous solution of potassium hydride, and gelling agent whichinitially gels the negative electrode mixture 5 and then causes zincparticles to be dispersed in the electrolytic solution evenly.

[0039] The battery can 2 internally stores the positive electrode 3 andthe separator 4 filled with the negative electrode mixture 5. Anaperture of the battery can 2 is coupled with the sealing member 6 forsealing the aperture. The sealing member 6 is made of plastic material.Further, by way of concealing the sealing member 6, the washer 7 and thenegative electrode terminal plate 8 are secured to the sealing member 6.Further, the current collecting pin 9 made of brass is inserted into athrough-hole of the sealing member 6 secured with the washer 7 from theupper position.

[0040] By way of inserting the nail-form current-collecting pin 9 weldedto the negative electrode terminal plate 8 into a through-hole formed atthe center of the sealing member 6, the current-collecting pin 9 reachesthe negative electrode mixture whereby enabling the negative electrodeto collect current. By way of connecting the positive electrode 3 to thebattery can 2, the positive electrode can collect current. Externalcircumferential surface of the battery can 2 is fully concealed by anexternal label (not shown). A positive electrode terminal is positionedto the bottom of the battery can 2.

[0041] The inventive battery comprising the above structural componentsgenerates own positive electrode reaction, negative electrode reaction,total reaction, and theoretical electromotive force by way of thefollowing:

[0042] Positive electrode reaction: NiOOH+H₂O+e ⁻→Ni(OH)₂+OH⁻

E₀=0.49 V

[0043] Negative electrode reaction: Zn+20H⁻→ZnO+H₂O+2e ⁻

E₀=−1.25 V

[0044] Total reaction: 2NiOOH+Zn+H₂O→2Ni (OH)₂+ZnO

[0045] Theoretical electromotive force: E₀=1.74 V

[0046] As is clear from the above chemical formulas, nickel hydride andzinc oxide are respectively generated from nickel oxyhydroxide and zincvia discharge reaction.

[0047] Nickel oxyhydroxide for composing a positive electrode activematerial is used for composing activating material of secondarybatteries such as a nickel-hydrogen battery and a nickel-cadmiumbattery. It is well known that these batteries proved surpassingdischarge performance. Nickel oxyhydroxide includes two kinds consistingof beta-type and gamma-type. Normally, these components can easily begenerated by way of electrolytically oxidizing nickel hydroxide viaso-called electrolytic oxidizing method. Nevertheless, the synthesizednickel oxyhydroxide, in particular, the beta-type nickel oxyhydroxidegenerates substantial self-discharge to result in the generation ofoxygen gas, and thus, in terms of storage characteristic and resistantcharacteristic against leakage of electrolytic solution, the beta-typenickel oxyhydroxide is not desired for use. To compensate for this, inorder to use the beta-type nickel oxyhydroxide for composing activematerial of the primary batteries, it is essential that self-dischargerate be lowered effectively. As a solution for this, conventionally,gamma-type nickel oxyhydroxide with less self-discharge rate has beenused against the beta-type nickel oxyhydroxide.

[0048] It is conceived that self-discharge and the resultant generationof oxygen are caused by decomposition of ion substance such as NO₃ ⁻ andCO₃ ²⁻ present in its crystal occurred inside of the battery. Such anion substance remains inside of crystal as impurities in the course ofproducing nickel oxyhydroxide. It is conceived however thatself-discharge characteristic of nickel oxyhydroxide can be improved byway of decreasing the above impurities.

[0049] On the other hand, it is also conceived that the deterioration ofthe storage characteristic of nickel oxyhydroxide is caused by dilutedelectrolytic solution, where dilution of electrolytic solution is causedby solidification of alkaline cation present in the electrolyticsolution within lattice via infiltration of alkaline cation betweenlayers of nickel oxyhydroxide relative to passage of time. Note thatnickel oxyhydroxide itself is multi-layer compound constituted withcadmium iodide crystals.

[0050] Based on the above conception, according to the findings ofinventors, initially, by applying a chemical oxidizing method to causenickel oxyhydroxide to be oxidized in chemical solution containing asuitable oxidizing agent such as sodium hypochlorite and a suitablealkaline substance such as lithium hydroxide, sodium hydroxide, andpotassium hydroxide, for example, nickel oxyhydroxide was synthesized.

[0051] It was found that, in the course of synthesizing nickeloxyhydroxide, independently of the kind including gamma and beta types,the above-referred ion of impurities flowed into the synthesizingsolution from the crystals to result in the generation of such nickeloxyhydroxide with decreased self-discharge characteristic and improvedsuitability for composing active material of the primary batteries.

[0052] Oxidation reaction generated in the above experiment is expressedby way of the following:

2Ni(OH)₂+ClO⁻→2NiOOH+Cl⁻+H₂O

[0053] Note that, depending on pH value in the chemical solution, typeof the resultant nickel oxyhydroxide differs. More particularly, whenthe pH value is less than a certain value, high-density beta-type nickeloxyhydroxide with 4.68 g/cm³ of theoretical density is generated. On theother hand, when the pH value exceeds a certain value, low-densitygamma-type nickel oxyhydroxide with 3.79 g/cm³ of theoretical density isgenerated. In the nickel-zinc battery 1 related to the presentinvention, in order to secure a greater capacity for the battery, amongthe above-referred nickel oxyhydroxides generated via the above-referredchemical oxidizing method, it is preferred that high-density beta-typenickel oxyhydroxide be used for composing positive electrode activematerial.

[0054] It is further desired that high-density nickel hydroxidecomprising substantially spherical particles be used for a starting rawmaterial. Normally, conventional nickel hydroxide comprisesnon-spherical particles each having 1.4˜1.8 g/cm³ of tap density and1.0˜1.4 g/cm³ of bulk density. On the other hand, the above-referredhigh-density nickel hydroxide comprises substantially sphericalparticles each having 2.0˜2.5 g/cm³ of tap density and 1.4˜1.8 g/cm³ ofbulk density respectively being higher than those of conventional nickelhydroxide.

[0055] Method of measuring the tap density and the bulk density isdescribed below. Initially, objective powder particles are fed into aspecific container via natural fall. Assuming that mass is expressed byA(g), volume B(cm³), and another volume is C(cm³) after softly tappingbottom of the lifted container 200 times against a desk, then, the bulkdensity and the tap density are defined by formulas shown below.

Bulk density=A/B (g/cm³)

Tap density=A/C (g/cm³)

[0056] It is desired that the tap density and the bulk density ofbeta-type nickel oxyhydroxide for forming positive electrode activematerial specified in the embodiment of the present invention shallremain in a range defined below. More particularly, the tap density ofthe beta-type nickel oxyhydroxide shall remain in a range of 2.2˜2.7g/cm³, whereas the bulk density of the beta-type nickel oxyhydroxideshall remain in a range of 1.6˜2.2 g/cm³. This is because, if the tapdensity and the bulk density remain less than the lower limit values, itis quite difficult to expand discharge capacity, and yet, it is quitedifficult to produce such beta-type nickel oxyhydroxide having greatervalues of the tap density and the bulk density beyond the upper limit ofthe defined ranges.

[0057]FIG. 2A exemplifies the inventive beta-type nickel oxyhydroxidecomprising substantially spherical particles. FIG. 2B exemplifiesconventional beta-type nickel oxyhydroxide comprising non-sphericalparticles. The upper side shown in FIGS. 2A and 2B designatesphotographs of the inventive beta-type nickel oxyhydroxide and theconventional beta-type nickel oxyhydroxide taken via an electronicmicroscope. Photographs shown in the lower side designate external formof particles shown in the upper side.

[0058] As shown in FIG. 2A, the inventive beta-type nickel oxyhydroxidecomprises substantially spherical particles. More particularly, particlesurface is relatively smooth without presence of projections. Althoughthere are some of slender and flat particles, as a whole, particles aresubstantially spherical.

[0059] On the other hand, as shown in FIG. 2B, conventional beta-typenickel oxyhydroxide comprises non-spherical particles showing such aform crushed into powder from a large mass, where each particle issquarish, and yet, there are a variety of forms including flat form,slender form, and substantially cubic form.

[0060]FIG. 3 exemplifies an example of grading distribution of theinventive beta-type nickel oxyhydroxide. It is desired that theinventive beta-type nickel oxyhydroxide for composing a positiveelectrode active material for implementing the present invention shallremain within such a mean particle size and a grading distributionspecified below. More particularly, it is desired that the inventivebeta-type nickel oxyhydroxide shall remain in a range of 19˜40 μm ofmean particle size. This is because, if the mean particle size is lessthan 19 μm or beyond 40 μm, it causes production of batteries to becomequite difficult. It is further desired that the inventive beta-typenickel oxyhydroxide shall remain in a range of 5˜80 μm of the gradingdistribution.

[0061] It is further desired that mean particle size of the beta-typenickel oxyhydroxide shall remain in a range of 19˜25 μm and the gradingdistribution shall remain in a range of 5˜70 μm.

[0062] Here, minimum and maximum values of the grading distribution aredefined as follows: when 5% of the entire grading values are a value orless than the value, the value is defined to be the minimum value, andwhen 95% of the entire grading value are a value or less than the value,the value is defined to be the maximum value.

[0063] When producing the beta-type nickel oxyhydroxide in accordancewith the above method by applying high-density nickel hydroxide as astarting raw material, it is possible to produce such nickel hydroxidewith higher tap density and higher bulk density to facilitate expansionof battery capacity.

[0064] Further, it is also desired that specific surface area of thebeta-type nickel oxyhydroxide based on the BET method shall remain in arange of 3˜50 m²/g. If the specific surface area based on the BET methodis less than 3 m²/g., it will result in the difficulty to expanddischarge capacity when discharging large current in particular.Conversely, if the specific surface area based on the BET method exceeds50 m²/g., even the beta-type nickel oxyhydroxide has a relatively largeamount of self-discharge, which results in difficulty in securingsufficient storage characteristic.

[0065] Further, by way of mixing beta-type nickel oxyhydroxide yieldedfrom nickel hydroxide via chemical oxidation process with such anaqueous solution (devoid of oxidizing agent) comprising one kind amonglithium hydroxide, sodium hydroxide, and potassium hydroxide, or twokinds or more than two kinds selected therefrom, and then, by causingalkaline cation to infiltrate into interface of layers of beta-typenickel oxyhydroxide, the inventors discovered that such beta-type nickeloxyhydroxide having such a storage characteristic surpassing that ofconventional beta-type nickel oxyhydroxide was secured while preservinghigh-density proper to the beta-type nickel oxyhydroxide.

[0066] It is desired that composition of alkaline cation in thebeta-type nickel oxyhydroxide generated via the above method shallremain in a range of 2˜5% by weight. It is further preferred that thecomposition of alkaline cation shall remain in a range of 3˜5% byweight. If the composition is less than 2% by weight, then, the amountof alkaline cation infiltrated between layers of the beta-type nickeloxyhydroxide will become short whereby storage characteristic can hardlybe improved. Although a greater amount of alkaline cation may be able toinfiltrate between layers by applying higher pressure via an autoclave,for example, if the composition of alkaline cation exceeds 5% by weight,then, the above beta-type nickel oxyhydroxide will be transmuted intolow-density gamma-type nickel oxyhydroxide to lose own high-density ofthe positive electrode active material.

[0067]FIG. 4 exemplifies the relationship between the composition ofpotassium in the beta-type nickel oxyhydroxide after being treated withaqueous solution of potassium hydroxide and the diffraction figure ofpowder via an X-ray treatment.

[0068] The X-ray diffraction patterns shown in FIG. 4A and FIG. 4Bdesignate patterns of the beta-type nickel oxyhydroxide. These drawingsrepresent that nickel oxyhydroxide still preserves the beta-form whenthe contents of potassium ion is less than 5% by weight. The X-raydiffraction patterns shown in FIG. 4C and FIG. 4D designate patterns ofthe gamma-type nickel oxyhydroxide. It is thus understood that thebeta-type nickel oxyhydroxide is transmuted into the gamma-type nickeloxyhydroxide when the contents of potassium ion exceeds 6% by weight.

[0069] When utilizing nickel oxyhydroxide as a positive electrode activematerial, there is a technical problem to solve because nickeloxyhydroxide and nickel hydroxide generated from nickel oxyhydroxide viadischarge respectively contain a low degree of electron conductivity.Accordingly, in order to promote utility of the positive electrodeactive material, it is preferred to mix graphite powder with thepositive electrode mixture. On the other hand, when forming such anickel-zinc battery comprising “inside-out” structure by way ofproviding external circumference of the nickel-zinc battery with apositive electrode comprising the blend of nickel oxyhydroxide at leastmixed with graphite powder formed into a hollow-cylindricalconfiguration in particular, and yet, by way of providing the centerportion with a gelled negative electrode comprising the blend of zincfor composing negative electrode active material, electrolytic solution,which are at least mixed with gelling agent, and yet, by way of furtherdisposing a separator between the positive electrode and the negativeelectrode, inventors discovered that desirable contents of graphitepowder against total weight of the positive electrode ranged from 4% byweight to a maximum of 8% by weight.

[0070] When there is less than 4% by weight of the contents of graphitepowder, it will not be able to fully improve electron conductivity inthe positive electrode. On the other hand, when there is more than 8% byweight of the contents of graphite powder, although electronconductivity in the positive electrode can be promoted to full extent,amount of nickel oxyhydroxide to be filled in the positive electrode asactivating material decreases to result in the contracted capacity ofthe battery. By way of properly arranging the contents of graphitepowder to be mixed in the positive electrode mixture, the nickel-zincbattery 1 realized by the present invention can secure optimal electronconductivity and storage capacity throughout service life.

[0071] EXAMPLE

[0072] Next, concrete examples for implementing the present inventionare described below. It should be understood however that the scope ofthe present invention is not solely limited to the following examples.

[0073] First, physical characteristics of nickel oxyhydroxide aredescribed below.

[0074] Initially, by way of chemically oxidizing electrolyzed manganesedioxide and high-density nickel hydroxide, a first beta-type nickeloxyhydroxide was generated. The above high-density nickel hydroxide wascomposed of substantially spherical particles based on 2.3 g/cm³ of tapdensity and 1.8 g/cm³ of bulk density. The above first beta-type nickeloxyhydroxide was composed of substantially spherical particles based on2.5 g/cm³ of tap density; 2.0 g/cm³ of bulk density, 20 μm of meanparticle size; and 5˜70 μm of grading distribution. The above chemicaloxidation was executed in alkaline solution containing sodiumhypochlorite. Next, a gamma-type nickel oxyhydroxide was generated bychemically oxidizing in the same manner as described above. The abovegamma-type nickel oxyhydroxide was composed of substantially sphericalparticles based on 1.8 g/cm³ of tap density and 1.6 g/cm³ of bulkdensity. Next a second beta-type nickel oxyhydroxide was generated bychemically oxidizing a gamma-type nickel oxyhydroxide and conventionalnickel hydroxide. The second beta-type nickel oxyhydroxide was composedof non-spherical particles based on 1.8 g/cm³ of tap density and 1.4g/cm³ of bulk density. Next, based on the composition specified in FIG.11, the first beta-type nickel oxyhydroxide, the gamma-type nickeloxyhydroxide, the second beta-type nickel oxyhydroxide, graphiteparticles, and 40% by weight of aqueous solution of potassium hydride,were fully mixed with each other to complete formulation of the positiveelectrode active agent. Next, the prepared positive electrode activeagents were pressurized by applying identical condition to mold theminto a hollow cylindrical configuration before completing the positiveelectrodes related to the present invention. Note that the mixedgraphite had 6 μm of mean particle size, 1˜25 μm of gradingdistribution, and a maximum of 0.3% by weight of ash component, asformulated into high-purity powder particles.

[0075] Initially, the positive electrode component was inserted in abattery can. Next, a separator comprising a polyolefin non-woven fabriccomplete with hydrophilic treatment was inserted into the positiveelectrode component. After feeding about 1g of electrolytic solution,gelled negative electrode mixture comprising mixture of zinc, gellingagent, and electrolytic solution was further inserted into the batterycan. Finally, aperture of the battery can was sealed with a sealingmember attached with a washer and a current-collecting pin beforecompleting production of alkaline batteries conforming to “AA”-sizeformat as samples 1˜4.

[0076]FIG. 11 represents composition (% by weight) of componentmaterials for constituting the positive electrode and filling amount (g)of positive electrode mixture per nickel-zinc battery. Sample 1represents an alkaline-manganese battery. Sample 2 represents anickel-zinc battery using beta-type nickel oxyhydroxide generated viachemical oxidation of high-density nickel hydroxide (this is referred toas a first beta nickel-zinc battery henceforth). Sample 3 represents anickel-zinc battery using gamma-type nickel oxyhydroxide generated viachemical oxidation of high-density nickel hydride (this is referred toas a gamma nickel-zinc battery henceforth). Sample 4 represents anickel-zinc battery using beta-type nickel oxyhydroxide generated viachemical oxidation of conventional nickel hydroxide (this is referred toas a second beta nickel-zinc battery). Note that filling amount ofpositive electrode mixture per battery differs between respectivesamples. This is because density of the used positive electrode activematerial differs between respective samples.

[0077] Next, those batteries corresponding to samples 1˜4 were subjectto a discharge test and a loading test. The discharge test was conductedby way of executing discharge until battery voltage descended to 1.0 Vat 1500 mW of constant power. To execute the loading test, commerciallyavailable digital cameras (“CAMEDIA C-2000 ZOOM” with a zoom lens, aproduct and a registered trade name of Olympus Optical Co., Ltd., Tokyo,Japan, each being fitted with a LCD monitor screen and using four of“AA”-size batteries), were utilized. The loading test was executed bycounting the number of still shots under still-photographic mode at 20°C. via an LCD monitoring screen without strobe-flashing at every minute.

[0078] Discharge curve and discharge capacity of the sample batteries1˜4 are respectively shown in FIG. 5 and FIG. 12. Test result vialoading of sample batteries 1˜4 in the digital cameras is shown in FIG.6.

[0079] By referring to FIG. 12 and FIG. 5, it is understood that,compared to the alkaline manganese battery corresponding to sample 1,the first beta nickel-zinc battery corresponding to sample 2, the gammanickel-zinc battery corresponding to sample 3, and the second betanickel-zinc battery corresponding to sample 4 respectively generatequite distinguished discharge characteristic under heavy load. Further,as shown in FIG. 6, it is also understood that those batteriescorresponding to samples 2˜4 are respectively durable to use for alonger period of time than the alkaline-manganese battery correspondingto sample 1 even when actually being loaded in a compact-size portableelectronic apparatus.

[0080] Compared to the gamma nickel-zinc battery as sample 3 and thesecond beta nickel-zinc battery as sample 4, the first beta nickel-zincbattery as sample 2 generates more distinguished dischargecharacteristic. Inasmuch as the nickel oxyhydroxide contained in thesample 2 is of the highest density, it is thus conceived that the sample2 contains a greater weight of positive electrode mixture per batterythan that of the samples 3 and 4, in other words, the sample 2 containsa greater capacity of the positive electrode.

[0081] Next, specific surface area of the positive electrode activematerial is described below.

[0082] Initially, beta-type nickel oxyhydroxide comprising substantiallyspherical particles were generated by chemically oxidizing high-densitynickel hydroxide, where the high-density nickel hydroxide was composedof substantially spherical particles based on 2.3 g/cm³ of tap densityand 1.8 g/cm³ of bulk density; the above chemical oxidizing process wasexecuted in alkaline solution containing sodium hypochlorite. A varietyof beta-type nickel oxyhydroxides with specific surface area in a rangeof 1˜60 m²/g based on BET method were prepared. Next, based on 85:8:7 ofweight ratio, the prepared beta-type nickel oxyhydroxides, graphite, andaqueous solution of potassium hydride (40% by weight), were fully mixedwith each other before completing production of positive electrodemixture. Like the preceding sample 2, a number of “AA”-size formatcompact alkaline batteries were prepared as samples 5˜20.

[0083] In addition, as in the above description, gamma-type nickeloxyhydroxides were generated by chemical oxidation. A variety ofgamma-type nickel oxyhydroxide with specific surface area in a range of3˜50 m²/g based on BET method were prepared. Except for those which wereused for composing a positive electrode active material, as in thesample 3, “AA”-size format alkaline batteries were prepared as Samples21˜24.

[0084] In addition, by electrolytically oxidizing conventional nickelhydroxide, a variety of beta-type nickel oxyhydroxides having specificsurface area in a range of 3˜50 m²/g based on BET method were prepared.Except for those which were used for composing positive electrode activematerial, like the preceding sample 4, “AA”-size format compact alkalinebatteries were prepared as samples 25˜28.

[0085] Next, discharge test was executed against the prepared samples5˜28 by continuously discharging voltage until reaching 1.0 V at 1500 mWof constant power at 20° C. of atmospheric temperature. One of thedischarge tests was executed against those sample batteries aged for twoweeks at 20° C. after the formation of batteries. Other tests wereexecuted against those which were stored for 20 days at 60° C. ofatmosphere after elapsing two weeks of initial storage period at 20° C.from the date of completing production thereof.

[0086] Results of discharge test executed against samples 5˜28 are shownin FIG. 13 and FIGS. 7˜9.

[0087] By referring to FIG. 13 and FIGS. 7˜9, as a result of testingsamples 5˜20 comprising beta-type nickel oxyhydroxides for composing apositive electrode via chemical oxidation process, it is understood thatsamples 7˜18 utilizing beta-type nickel oxyhydroxide each having 3˜50m²/g of specific surface area based on BET method respectively generatequite distinguished discharge characteristic under heavy load anddurable storage characteristic. On the other hand, despite ofsatisfactory storage characteristic, those samples 21˜24 utilizinggamma-type nickel oxyhydroxide for composing a positive electrode viachemical oxidation process respectively fail to generate distinguisheddischarge characteristic under heavy load. Conversely, despite ofsufficient discharge characteristic under heavy load, those samples25˜28 utilizing beta-type nickel oxyhydroxide for composing positiveelectrode via electrolytic oxidation process respectively prove to benoticeably poor in the storage durability.

[0088] Based on the above results, it is understood that, in terms ofthe nickel-zinc battery related to the present invention, beta-typenickel oxyhydroxide generated via chemical oxidation of high-densitynickel hydroxide should desirably be utilized for composing positiveelectrode active material. It is further understood that use of such abeta-type nickel oxyhydroxide having own specific surface area within arange of 3˜50 m²/g via BET method is desirable.

[0089] Next, a method of treating beta-type nickel oxyhydroxide inalkaline solution is described below.

[0090] Initially, beta-type nickel oxyhydroxide generated by chemicaloxidation of high-density nickel hydroxide was mixed with aqueoussolution of potassium hydroxide, and then, adjustment was effectedagainst density of aqueous solution of potassium hydroxide, mixingtemperature, mixing time, and mixing pressure. It was so arranged thatnet contents of potassium in the final formulation of the beta-typenickel oxyhydroxide precisely range from 0.5% by weight to a maximum of5.0% by weight. Note that the above-referred high-density nickelhydroxide was composed of substantially spherical particles based on 2.3g/cm³ of tap density and 1.8 g/cm³ of bulk density. The above chemicaloxidation process was executed in alkaline solution containing sodiumhypochlorite. The resultant beta-type nickel oxyhydroxide was composedof substantially spherical particles each having 20 μm of mean particlesize based on 2.5 g/cm³ of tap density, 2.0 g/cm³ of bulk density, and5˜70 μm of grading distribution. The processing condition is shown inFIG. 14.

[0091] During the test, whenever pressurizing process was required,reaction is implemented via an autoclave. The beta-type nickeloxyhydroxide and potassium hydroxide (40% by weight) prior to treatmentwere arranged to be 1:5 of weight ratio. After completing the treatment,separation and washing were executed against the beta-type nickeloxyhydroxide.

[0092] It is desired that concentration of potassium hydroxide be in arange from 30% by weight to a maximum of 45% by weight. If concentrationof potassium remains below 30% by weight, then it will become difficultto terminate reaction. On the other hand, it is quite hard to procuresuch potassium hydroxide aqueous solution having more than 45% by weightof concentration from industrial sources.

[0093] Assuming that potassium hydroxide has 40% by weight ofconcentration for example, in terms of weight ratio between beta-typenickel oxyhydroxide and potassium hydroxide prior to the treatment, itis desired that weight ratio of potassium hydroxide remain within arange from 3 to 10 against 1 of that of beta-type nickel oxyhydroxide.This is because, if the weight ratio is less than 3, then, it willbecome difficult to terminate reaction. Conversely, if the weight ratioexceeds 10, it will entail difficulty to separate and wash the beta-typenickel oxyhydroxide after completing a reaction process. Further, as isobvious from FIG. 14, it is desired that reaction temperature be heldwithin a range of 40° C.˜60° C. Further, it is also desired thatreaction time be held within a range of approximately 10 hours˜60 hours.Further, it is also desired that reaction pressure be held within arange from normal pressure to a maximum of 0.9 Mpa.

[0094] Test result evidenced that the form of the beta-type nickeloxyhydroxide impregnated with alkaline cation between layers producedvia the above-referred alkaline treatment was substantially identical tothat of the other beta-type nickel oxyhydroxide generated via chemicaloxidation of high-density nickel hydroxide.

[0095] Further, test result evidenced that mean particle size, gradingdistribution, bulk density, and tap density of the beta-type nickeloxyhydroxide containing alkaline cation were substantially identical tothose of the other beta-type nickel oxyhydroxide generated via chemicaloxidation of high-density nickel hydroxide.

[0096] Next, based on the composition shown in FIG. 15, a positiveelectrode mixture was prepared by fully mixing the beta-type nickeloxyhydroxide generated via chemical oxidation of high-density nickelhydroxide, the other beta-type nickel oxyhydroxide generated via analkaline treatment process, graphite powder, and aqueous solution ofpotassium hydroxide. Note that the graphite power is formulated ashigh-purity graphite powder comprising 6 μm of mean particle size, 1˜25μm of grading distribution, and a maximum of 0.3% by weight of ashcomponent. Then, like the above example, a number of “AA”-size formatalkaline batteries were produced as samples 29˜39.

[0097] Sample 29 was prepared with the beta-type nickel oxyhydroxidegenerated via chemical oxidation of high-density nickel hydroxide.Samples 30˜39 were respectively prepared with the other beta-type nickeloxyhydroxide complete with the above alkaline treatment. FIG. 15designates composition (% by weight) of component materials forcomposing the positive electrode, composition (% by weight) of potassiumdispersed in the beta-type nickel oxyhydroxide, and filling amount(gram) of the positive electrode mixture per battery. Composition (% byweight) of potassium dispersed in the beta-type nickel oxyhydroxide wasquantitatively analyzed by applying an atomic light-absorptive analysismethod.

[0098] Those batteries corresponding to samples 29˜39 were then storedfor 20 days at 60° C., and then treated with a discharge test until thevoltage reached 1.0 V at 100 mW, 500 mW, 1000 mW, and 1500 mW ofconstant power. Discharge capacity of batteries corresponding to samples29˜39 before and after storage is shown in FIG. 16, FIG. 17, and FIG.10.

[0099] By referring to FIG. 16 and FIG. 10, it is evidenced that thosebatteries corresponding to samples 29˜39 prior to storage respectivelygenerated a substantially identical value of discharge capacity at 100mW, 500 mW, 1000 mW, and 1500 mW of constant power.

[0100] By referring to FIG. 16, FIG. 17, and FIG. 10, it is understoodthat, compared to the sample 29 comprising the beta-type nickeloxyhydroxide generated via chemical oxidation of high-density nickelhydroxide, the sample 33 incorporating more than 2% by weight ofpotassium in the beta-type nickel oxyhydroxide incurred less degradationof capacity after storage as a result of treatment with alkalinesolution. It was further clarified from the test results of samples35˜39 that further degradation of capacity could be prevented fromoccurrence by way of providing a minimum of 3% by weight of potassiumcomposition. When there is a maximum of 2% by weight of potassiumcomposition in the beta-type nickel oxyhydroxide, improved effect canhardly be generated in the storage characteristic of batteries.Conceivably, inasmuch as the amount of potassium ion infiltrated betweenlayers of the beta-type nickel oxyhydroxide via an alkaline treatmentremains short, potassium ion present in electrolytic solution isabsorbed into the beta-type nickel oxyhydroxide during storage, wherebycausing concentration of the electrolytic solution to be diluted.

[0101] The above description has solely referred to the case in whichaqueous solution of potassium hydroxide was utilized for executing analkaline treatment process. However, according to the test result,substantially identical results were also generated even when utilizingaqueous solution of lithium hydroxide and aqueous solution of sodiumhydroxide as well. Based on this result, it is conceived thatsubstantially identical results will also be secured even when utilizingthese alkaline aqueous solutions via mixture and even when more than twokinds of alkaline cations are mixed together inside of the lattice ofthe beta-type nickel oxyhydroxide.

[0102] Based on the above result, in the formation of the nickel-zincbattery according to a preferred form for embodying the presentinvention, it is clarified from the process for enabling alkalinecationic seed to infiltrate itself between layers of the beta-typenickel oxyhydroxide that composition of the alkaline cationic seed aftercompletion of the process should desirably be arranged to be in a rangefrom 2% by weight to a maximum of 5% by weight, more preferably, in arange from 3% by weight to a maximum of 5% by weight before utilizingthe beta-type nickel oxyhydroxide to serve as the positive electrodeactive material.

[0103] The above description related to the above-referred alkalinetreatment has solely referred to the beta-type nickel oxyhydroxidecomprising substantially spherical particles. It should be understood,however that the form of the beta-type nickel oxyhydroxide is not solelylimited to the above substantially spherical configuration, but thepresent invention is also applicable to a variety of forms other thanthe spherical configuration as well.

[0104] Next, the amount of contents of graphite formulated in thepositive electrode mixture is described below.

[0105] Initially, based on the composition shown in FIG. 18, beta-typenickel oxyhydroxide generated via chemical oxidation of high-densitynickel hydroxide, graphite, and 40% by weight of aqueous solution ofpotassium hydroxide, were fully mixed with each other to producepositive electrode mixture, and then, like the above example, a numberof “AA”-size format alkaline batteries were produced as samples 40˜48.Note that the above beta-type nickel oxyhydroxide was composed ofsubstantially spherical particles each having 20 μm of mean particlesize, based on 2.5 g/cm³ of tap density, 2.0 g/cm³ of bulk density, and5˜70 μm of grading distribution. The above-referred high-density nickelhydroxide is composed of substantially spherical particles based on 2.3g/cm³ of tap density and 1.8 g/cm³ of bulk density. The above chemicaloxidation was executed in alkaline solution containing sodiumhypochlorite. The above graphite was formulated as high-purity graphitepowder comprising 6 μm of mean particle size, 1˜25 μm of gradingdistribution, and a maximum of 0.3% of ash component.

[0106] Like the preceding examples, those batteries corresponding tosamples 40˜48 were respectively treated with discharge test until thevoltage reached 1.0 V at 1500 mW of constant power. Test results ofdischarge capacity of the samples 40˜48 are shown in FIG. 19 and FIG.11.

[0107] By referring to FIG. 19 and FIG. 11, it was clarified that bettereffect was secured by adding a minimum of 4% by weight and a maximum of8% by weight of graphite against the total weight of the positiveelectrode as the proper amount to be included in the positive electrodemixture. Since nickel oxyhydroxide and nickel hydroxide as the onegenerated via discharge respectively contain a low degree of electronconductivity, it is conceived that, when the graphite contents are lessthan 4% by weight in the positive electrode mixture, such an effect forimproving electron conductivity in the positive electrode can not fullybe secured. On the other hand, when the graphite contents exceed 8% byweight, despite of enough effect to improve electron conductivity in thepositive electrode, as a result of the decreased filling amount ofnickel oxyhydroxide as the positive electrode active material, inconsequence, battery capacity itself is contracted.

[0108] Based on the above results, it was clarified that the amount ofgraphite to be included in the positive electrode mixture shoulddesirably be defined to be a minimum of 4% by weight and a maximum of 8%by weight against the total weight of the positive electrode.

[0109] Although the above description pertaining to practical aspectsfor embodying the present invention has solely referred to thenickel-zinc battery as a primary battery. It should be understoodhowever that the scope of the present invention is by no meansrestricted to the primary battery, but the scope of the presentinvention is also applicable to other nickel-zinc batteries serving as asecondary battery.

[0110] Further, the above description has also referred to a cylindricalnickel-zinc battery. However, the scope of the present invention is notsolely limited to the cylindrical battery, but the present invention isalso applicable to those nickel-zinc batteries with a flat shape andother shapes as well.

[0111] Further, it should also be understood that, not only theabove-referred practical aspects, but also the present invention mayalso introduce a variety of forms and constitutions within such a scopethat does not deviate from the essentials of the present invention.

What is claimed is:
 1. Beta-type nickel oxyhydroxide comprisingsubstantially spherical particles.
 2. The beta-type nickel oxyhydroxideaccording to claim 1, wherein mean particle size of said beta-typenickel oxyhydroxide remains in a range from 19 μm to a maximum of 40 μm.3. The beta-type nickel oxyhydroxide according to claim 2, whereingrading distribution of said beta-type nickel oxyhydroxide remains in arange from 5 μm to a maximum of 80 μm.
 4. The beta-type nickeloxyhydroxide according to any one of claims 1 and 2, wherein bulkdensity of said beta-type nickel oxyhydroxide remains in a range from1.6 g/cm³ to a maximum of 2.2 g/cm³, whereas tap density of saidbeta-type nickel oxyhydroxide remains in a range from 2.2 g/cm³ to amaximum of 2.7 g/cm³.
 5. The beta-type nickel oxyhydroxide according toany one of claims 1 and 2, wherein specific surface area based on BETmethod ranges from 3 m²/g to a maximum of 50 m²/g.
 6. Beta-type nickeloxyhydroxide containing alkaline cation disposed between layers thereof.7. The beta-type nickel oxyhydroxide according to claim 6, wherein saidbeta-type nickel oxyhydroxide comprises substantially sphericalparticles.
 8. The beta-type nickel oxyhydroxide according to claim 6,wherein said alkaline cation substance comprises any one of or acombination of more than two selected from a group of Li+, Na+, and K+.9. The beta-type nickel oxyhydroxide according to claim 6, wherein saidbeta-type nickel oxyhydroxide contains 2% by weight up to a maximum of5% by weight of alkaline cation.
 10. A method of producing beta-typenickel oxyhydroxide comprising a step of oxidizing nickel hydroxide inalkaline solution containing sodium hypochlorite.
 11. A method ofproducing beta-type nickel oxyhydroxide comprising; a step of initiallyoxidizing nickel hydroxide in alkaline solution containing sodiumhypochlorite; and a step of mixing yielded beta-type nickel oxyhydroxidein alkaline solution to cause alkaline cation to be disposed betweenlayers of said beta-type nickel oxyhydroxide.
 12. The method ofproducing beta-type nickel oxyhydroxide according to any one of claims10 and 11, wherein said nickel hydroxide comprises substantiallyspherical particles.
 13. The method of producing beta-type nickeloxyhydroxide according to any one of claims 10 and 11, wherein saidnickel hydroxide comprises substantially spherical particles each havingbulk density ranging from 1.4 g/cm³ to a maximum of 1.8 g/cm³ and tapdensity ranging from 2.0 g/cm³ to a maximum of 2.5 g/cm³.
 14. The methodof producing beta-type nickel oxyhydroxide according to claim 11,wherein said alkaline solution for having alkaline cation between layersof said beta-type nickel oxyhydroxide comprises any one of or acombination of more than two of alkaline salts selected from a groupcomprising lithium hydroxide, sodium hydroxide, and potassium hydroxide.15. A positive electrode active material comprising beta-type nickeloxyhydroxide, wherein said beta-type nickel oxyhydroxide comprisessubstantially spherical particles.
 16. The positive electrode activematerial according to claim 15, wherein mean particle size of saidbeta-type nickel oxyhydroxide ranges from 19 μm to a maximum of 40 μm.17. The positive electrode active material according to claim 16,wherein grading distribution of said beta-type nickel oxyhydroxideranges from 5 μm to a maximum of 80 μm.
 18. The positive electrodeactive material according to any one of claims 15 and 16, wherein bulkdensity of said beta-type nickel oxyhydroxide ranges from 1.6 g/cm³ to amaximum of 2.2 g/Cm³, whereas tap density of said beta-type nickeloxyhydroxide ranges from 2.2 g/cm³ to a maximum of 2.7 g/cm³.
 19. Thepositive electrode active material according to any one of claims 15 and16, wherein specific surface area of said beta-type nickel oxyhydroxidebased on BET method ranges from 3 m²/g to a maximum of 50 m²/g.
 20. Apositive electrode active material comprising beta-type nickeloxyhydroxide, wherein said beta-type nickel oxyhydroxide has alkalinecation between its own layers.
 21. The positive electrode activematerial according to claim 20, wherein said beta-type nickeloxyhydroxide comprises substantially spherical particles.
 22. Thepositive electrode active material according to claim 20, wherein saidalkaline cation substance comprises any one of or a combination of morethan two selected from a group comprising Li+, Na+, and K+.
 23. Thepositive electrode active material according to claim 20, wherein saidbeta-type nickel oxyhydroxide contains 2% by weight to a maximum of 5%by weight of alkaline cation substance therein.
 24. A nickel-zincbattery comprising; a positive electrode comprising mixed powdercontaining at least beta-type nickel oxyhydroxide being a positiveelectrode active material and graphite powder being an electricconductive agent; a negative electrode comprising gelled compoundcontaining at least zinc being a negative electrode active material,electrolytic solution, and gelling agent for uniformly dispersing saidzinc and electrolytic solution; and a separator being disposed betweensaid positive electrode and said negative electrode; wherein saidbeta-type nickel oxyhydroxide comprises substantially sphericalparticles.
 25. The nickel-zinc battery according to claim 24, whereinmean particle size of said beta-type nickel oxyhydroxide ranges from 19μm to a maximum of 40 μm.
 26. The nickel-zinc battery according to claim25, wherein grading distribution of said beta-type nickel oxyhydroxideranges from 5 μm to a maximum of 80 μm.
 27. The nickel-zinc batteryaccording to claim 24, wherein bulk density of said beta-type nickeloxyhydroxide ranges from 1.6 g/cm³ to a maximum of 2.2 g/cm³, whereastap density of said beta-type nickel oxyhydroxide ranges from 2.2 g/cm³to a maximum of 2.7 g/cm³.
 28. The nickel-zinc battery according toclaim 24, wherein specific surface area of said beta-type nickeloxyhydroxide based on BET method ranges from 3 m²/g to a maximum of 50m²/g.
 29. A nickel-zinc battery comprising: a positive electrodecomprising mixed powder containing at least beta-type nickeloxyhydroxide being a positive electrode active material and graphitepowder being an electric conductive agent; a negative electrodecomprising gelled compound containing at least zinc being a negativeelectrode active material, electrolytic solution, and gelling agent foruniformly dispersing zinc and electrolytic solution; and a separatorbeing disposed between said positive electrode and said negativeelectrode; wherein: said beta-type nickel oxyhydroxide has alkalinecation between its own layers.
 30. The nickel-zinc battery according toclaim 29, wherein said beta-type nickel oxyhydroxide comprisessubstantially spherical particles.
 31. The nickel-zinc battery accordingto claim 29, wherein said alkaline cation substance comprises any one ofor a combination of more than two selected from a group comprising Li+,Na+, and K+.
 32. The nickel-zinc battery according to claim 29, whereinsaid beta-type nickel oxyhydroxide contains 2% by weight to a maximum of5% by weight of alkaline cation substance therein.
 33. The nickel-zincbattery according to any one of claims 24 and 29, wherein said positiveelectrode is molded into a hollow cylindrical configuration and disposedon an external peripheral portion; said negative electrode in gelledform is disposed at a center portion, whereas said separator is disposedbetween said positive electrode and said negative electrode, wherebyforming an “inside-out” structure.
 34. The nickel-zinc battery accordingto any one of claims 24 and 29, wherein said positive electrode contains4% by weight to a maximum of 8% by weight of graphite powder against owntotal weight of said positive electrode.